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Exploring Our Ecosystem!

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Exploring Our Ecosystem!

You are part of a kaitiaki team investigating a New Zealand estuary. Read the briefing, study the data, and use evidence to explain how living things and non-living parts of the ecosystem connect. Answer in your own words where asked.

Estuary briefing

An estuary is where freshwater from rivers mixes with seawater. At Te Awa Estuary, sunlight warms the shallow water and helps algae and seagrass grow. These producers make their own food. Snails and small crustaceans graze on algae and seagrass. Mud crabs eat small crustaceans, while juvenile fish eat crustaceans and sometimes snails. Herons catch juvenile fish. Decomposers such as bacteria break down dead organisms and waste, returning nutrients to the mud and water. The estuary’s salinity, water temperature, light, oxygen and muddy shelter are non-living factors that affect which organisms can thrive.

1.In one or two sentences, explain what an ecosystem is. Include both living things and at least one non-living factor from Te Awa Estuary.

2.Choose the best classification for each item: biotic (living or once-living) or abiotic (non-living). Items: seagrass, sunlight, mud crab, salinity, bacteria, dissolved oxygen.

Seagrass
Sunlight
Mud crab
Salinity
Bacteria
Dissolved oxygen

Biotic
Abiotic
Biotic
Abiotic
Abiotic
Biotic

3.Which option shows a plausible path of energy through the Te Awa Estuary food chain?

Sunlight → algae → small crustacean → juvenile fish → heron
Heron → juvenile fish → algae → sunlight
Mud crab → sunlight → snail → seagrass
Bacteria → heron → sunlight → small crustacean

4.Algae make their own food using sunlight. What role do algae play in this ecosystem, and why is that role important to other organisms?

5.Draw a food web using at least five organisms from the briefing. Use arrows to show the direction that energy moves (from the food to the organism that eats it). Include algae or seagrass, a grazer, a predator, and a decomposer.

Month

Small crustaceans counted

Juvenile fish counted

October

November

December

6.Use the monitoring grid. Between November and December, how did the counts of small crustaceans and juvenile fish change? Calculate the change in each count.

7.The small crustacean count fell between November and December, and the juvenile fish count also fell. Suggest one possible food-web explanation. Is this evidence enough to prove the cause?

8.“If a non-living factor changes, it can affect living organisms in an ecosystem.” State true or false and give one example from the estuary briefing.

TrueFalse

9.Bacteria break down dead organisms and waste in the estuary. Explain how this helps nutrients become available again in the ecosystem.

10.Imagine runoff from nearby land makes the estuary water cloudy, reducing the light reaching seagrass. Predict one possible effect on the food web and suggest one practical action people could take to help reduce runoff.